During operation of a boat powered by an outboard motor, it is often desirable to raise or lower the motor. For example, when operating a boat in shallow water or removing a boat from the water with a submersible boat trailer, it is often necessary to raise the motor so that the propeller and rudder are not damaged by the bottom of the body of water. In other instances, it may be desirable to raise the motor while operating the boat at high speeds to reduce the amount of drag created by the presence of the motor in the water.
Adjusting the trim or height of an outboard motor can be accomplished by manipulating a set of controls operably connected to a jack plate. Although meanings of the term jack plate can vary, for purposes of this application, jack plate refers to the interfacing apparatus between a boat and an accompanying outboard motor. Generally, a component of the jack plate is fixedly mounted to the transom of the boat, while another component is mounted to the outboard motor. By operating an actuator attached to the two components, the motor can be raised or lowered in relation to the transom. A number of different types of lift actuators have been incorporated into jack plates, such as, for example, hydraulic, electric, electro-mechanical, or strictly manually operated actuators.
Jack plates can accomplish raising or lowering the propeller of an outboard motor by pivoting the motor about a selected point, such as at or near the top of the transom. Pivoting an outboard motor to raise the motor, however, has several drawbacks. As the motor pivots, the angle at which the propeller displaces water changes, resulting in a decrease in the propulsive efficiency of the motor.
Because of the drawbacks associated with tilting outboard motors, jack plates have been developed that can raise or lower the entire outboard motor in a substantially vertical direction. For example, U.S. Pat. No. 8,627,779 and U.S. Pat. No. 8,267,025, both of which are incorporated herein by reference, show an actuator-powered jack plate having a transom plate mountable to a boat transom and a motor lift plate movable substantially vertically with respect to the transom plate. The larger the motor mounted to the motor lift plate, the greater the load that must be accommodated by the actuator to raise and lower the motor with respect to the boat. Accordingly, more powerful and/or more durable actuators have been called for to maintain performance over time with larger motors. It would be desirable to reduce the size of such actuators while still maintaining performance, reliability, and life of such actuators.